Q1: Which of the following is an example of a weak electrolyte? (a) Sodium chloride (b) Sulphuric acid (c) Acetic acid (d) Potassium hydroxide
Solution:
Ans: (c) Acetic acid is a weak electrolyte as it is feebly ionised in solution and acts as a poor conductor of electricity, unlike strong electrolytes.
Q2: What is the process of converting electrical energy into chemical energy called? (a) Electrochemical cell (b) Electrolytic cell (c) Ionisation (d) Dissociation
Solution:
Ans: (b) An electrolytic cell is a device specifically designed to convert electrical energy into chemical energy through the process of electrolysis.
Q3: During electrolysis of acidified water, which gas is produced at the cathode? (a) Oxygen (b) Chlorine (c) Hydrogen (d) Sulphur dioxide
Solution:
Ans: (c) Hydrogen ions gain electrons at the cathode forming hydrogen atoms which combine to form hydrogen gas molecules during electrolysis of acidified water.
Q4: In electroplating, the article to be electroplated is always kept at the: (a) Anode (b) Cathode (c) In the electrolyte solution (d) Outside the cell
Solution:
Ans: (b) The article to be electroplated is connected to the cathode where positive metal ions from the electrolyte gain electrons and get deposited.
Q5: Which process involves the removal of oxygen or addition of hydrogen? (a) Oxidation (b) Reduction (c) Ionisation (d) Dissociation
Solution:
Ans: (b) Reduction is defined as a chemical process which involves either the removal of oxygen from a substance or the addition of hydrogen to it.
Fill in the Blanks
Q1: The electrode connected to the negative terminal of the battery is called _____.
Solution:
Ans: cathode
Q2: Atoms which carry a positive charge are called _____.
Solution:
Ans: cations
Q3: The process of extraction of metals by electrolysis is called _____.
Solution:
Ans: electrometallurgy
Q4: Compounds which neither in solution nor in molten state conduct electricity are called _____.
Solution:
Ans: non-electrolytes
Q5: The preferential discharge of ions at respective electrodes is known as _____ of ions.
Solution:
Ans: selective discharge
True or False
Q1: An electrochemical cell converts chemical energy into electrical energy.
Solution:
Ans: True An electrochemical cell is specifically designed as a device to convert chemical energy into electrical energy through chemical reactions.
Q2: Kerosene is an example of a strong electrolyte.
Solution:
Ans: False Kerosene is actually a non-electrolyte which does not allow electric current to pass through it in any state.
Q3: Oxidation is the process of addition of oxygen or removal of hydrogen.
Solution:
Ans: True Oxidation is defined as a chemical process involving either the addition of oxygen to or the removal of hydrogen from a substance.
Q4: During electrolysis of copper sulphate solution with copper electrodes, oxygen is liberated at the anode.
Solution:
Ans: False When copper electrodes are used, copper atoms from the anode lose electrons and go into solution, not oxygen liberation.
Q5: Ionisation is the process by which ionic compounds dissociate in fused state.
Solution:
Ans: False Ionisation refers to polar covalent compounds converting into ions in water, while dissociation refers to ionic compound separation.
Match the Following
Column A
Column B
1. Anode
A. Feebly ionised compounds
2. Reduction
B. Arrangement of metals based on electron loss
3. Weak electrolytes
C. Atoms carrying negative charge
4. Electrochemical series
D. Electrode connected to positive terminal
5. Anions
E. Removal of oxygen or addition of hydrogen
Solution:
Ans:
1 - D: Anode is the electrode that is connected to the positive terminal of the battery during electrolysis.
2 - E: Reduction is a chemical process involving the removal of oxygen from or the addition of hydrogen to substances.
3 - A: Weak electrolytes are compounds which are feebly ionised in solution and conduct electricity poorly.
4 - B: Electrochemical series arranges metals based on the ease with which their atoms lose electrons to form positive ions.
5 - C: Anions are atoms or groups of atoms which carry a negative electrical charge.
Short Answer Questions
Q1: Explain the difference between electrolytic dissociation and ionisation with suitable examples.
Solution:
Ans: Electrolytic dissociation is the process where ionic compounds like sodium chloride separate into ions in fused state or aqueous solution. For example, NaCl dissociates into Na+ and Cl- ions. Ionisation occurs when polar covalent compounds convert into ions in water solution. For example, HCl ionises into H+ and Cl- ions in water solution.
Q2: What are the factors that affect the selective discharge of ions during electrolysis?
Solution:
Ans: The selective discharge of ions depends on three main factors. Firstly, the relative position of ions in the electrochemical series determines which ion will discharge preferentially. Secondly, the concentration of ions in the electrolyte affects discharge. Thirdly, the nature of the electrode used also influences which ions will be discharged at the respective electrodes during electrolysis.
Q3: Describe the process and reactions occurring during electrolysis of acidified water.
Solution:
Ans: During electrolysis of acidified water using platinum electrodes, water ionises into H+ and OH- ions whilst sulphuric acid provides additional H+ and SO42- ions. At the cathode, hydrogen ions gain electrons forming hydrogen atoms which combine to produce hydrogen gas. At the anode, hydroxide ions lose electrons forming hydroxyl radicals which produce water and oxygen gas.
Q4: Why is electroplating carried out? Explain the basic principle involved in the process.
Solution:
Ans: Electroplating is carried out for decoration purposes and to protect metals from rusting and corrosion. The process involves depositing a thin film of a valuable metal like gold, silver or nickel on another metallic article using electricity. The article to be plated is kept at the cathode where metal ions gain electrons and get deposited on its surface.
Q5: Distinguish between strong electrolytes and weak electrolytes with examples.
Solution:
Ans: Strong electrolytes are compounds which are almost completely ionised in aqueous solution or fused state, allowing easy passage of electric current. Examples include mineral acids, alkalis and salts. Weak electrolytes are compounds which are feebly ionised and are poor conductors of electricity in fused state or aqueous solution. Examples include acetic acid and oxalic acid.
Long Answer Questions
Q1: Analyse the process of electroplating with nickel. Describe the electrolyte used, the reactions at both electrodes, and explain why the article must be placed at the cathode.
Solution:
Ans: Electroplating with nickel uses aqueous nickel sulphate solution as the electrolyte which dissociates into Ni2+ and SO42- ions. The article to be electroplated is kept at the cathode where nickel ions gain two electrons and get deposited as nickel metal. A block of pure nickel is used as the anode where nickel atoms lose electrons and go into solution as Ni2+ ions. The article must be at the cathode because metal deposition occurs there through reduction, ensuring a thin, uniform coating.
Q2: Evaluate the process of electrolytic refining of copper. Justify why impure copper is used as the anode and explain what happens to the impurities.
Solution:
Ans: Electrolytic refining of copper uses copper sulphate solution with dilute sulphuric acid as electrolyte. Impure copper serves as the anode whilst a thin strip of pure copper acts as the cathode. At the anode, copper atoms lose electrons forming Cu2+ ions which dissolve into the electrolyte. At the cathode, these Cu2+ ions gain electrons and deposit as pure copper. Impure copper is used at the anode because during electrolysis, only copper dissolves whilst impurities settle below as anode mud, achieving purification.
Q3: Compare the processes of oxidation and reduction. Explain the roles of oxidising agents and reducing agents with reference to electron transfer during electrolysis.
Solution:
Ans: Oxidation involves addition of oxygen or removal of hydrogen from substances, whilst reduction involves removal of oxygen or addition of hydrogen. Oxidising agents accept electrons or provide oxygen, thereby oxidising other substances. Reducing agents provide electrons, hydrogen or electropositive ions, thereby reducing other substances. During electrolysis, at the cathode, reduction occurs as cations gain electrons. At the anode, oxidation occurs as anions lose electrons. These complementary processes demonstrate that oxidation and reduction always occur simultaneously in electrochemical reactions.
The document Worksheet with Solutions: Electrolytes, Non-Electrolytes and Electrolysis is a part of the Class 10 Course Chemistry Class 10 ICSE.
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